Samuel Sia, of Columbia University, US, outlines the challenges in bringing cheap diagnostic devices to developing countries.

Microfluidics offers the hope of revolutionizing medical diagnostics in developing countries. By manipulating small amounts of fluids, microfluidics and related 'lab-on-a-chip' technologies promise to miniaturize and automate routine laboratory tests onto a handheld microchip. Such devices use minimal and low-cost equipment, and are only starting to emerge; by contrast, most microfluidic applications thus far have required accompanying equipment (such as pumps and microscopes) that are expensive, bulky, and mainly for use in rich research labs. Deploying lab-on-a-chip technology in the extremely resource-poor environment of developing countries is a challenge, and is motivating a rapidly emerging field of research.¹

Nowhere is the need for new diagnostic technologies greater than in developing countries, where people suffer disproportionately from infectious disease compared to the US and Europe. In addition to HIV/AIDS, malaria and tuberculosis, many neglected tropical diseases run rampant, for which early diagnosis brings enormous benefit. Garnering less public attention than infectious diseases is the rise of non-communicable disease (cardiovascular disease and cancer) in developing countries. These diseases, taking place in resource-poor environments, are also in need of new and creative diagnostic technologies.

In principle, microfluidics offer advantages that seem ideal to address this immense public health challenge. But even in the US and Europe, development of point-of-care microfluidic devices has proven difficult due to challenges in technology and market. Developing countries present a daunting array of design challenges: extreme low cost, low power consumption, poor public health infrastructure, and challenging environmental conditions. Each of these criteria must be considered in designing all procedures within the microsystem, from control of the fluids, detection of the signal, to disposal of the device. A successful design must also consider the specific environment of the end-use setting, from a rich national reference laboratory to a remote rural health dispensary.

So where does one start? Two classes of analytes under development are proteins and nucleic acids, which constitute the bulk of known biomarkers for infectious diseases. Several years ago, we developed an integrated low-cost and portable immunoassay for detecting protein biomarkers in developing countries, based on simple optical detection in a microfluidic device. Other approaches for immunoassays include electrical detection and surface plasmon resonance. Current methods for nucleic acid amplification tests include PCR and isothermal amplification in a microfluidic chip. In all these methods, fluid control and signal detection must be simple, automated, and extremely low-cost.

Other new diagnostic devices will be needed. Among them are devices for cell counting (most urgently, of CD4⁺ T-cells which instruct the administration of antiretroviral therapy for AIDS patients), microscopy (commonly used in blood smears for diagnosing malaria), and cell culture (for detecting bacterial infections).

The research field of lab-on-a-chip devices for global health is young and potentially richly rewarding. But it is sobering to reflect that in practice, few new diagnostic tests have been successfully introduced into developing countries - the lateral flow test, which uses immunochromatography on a nitrocellulose membrane to indicate the yes/no presence of antigens or antibodies (and is most familiar to us as the pregnancy strip test), has been the main success story. To be successful, it is prudent to engage at an early stage academic researchers, industrial partners, and non-profit and governmental organizations to negotiate the complex landscape of clinical testing, regulatory requirements, and distribution strategy. It will be interesting to monitor this research field (fueled by philanthropist organizations such as the Gates Foundation), which faces technological challenges but promises profound social impact.

Read Samuel Sia et al.'s critical review 'Lab-on-a-chip devices for global health: past studies and future opportunities' in January's issue of Lab on a Chip.